Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
Processing...

Test String

Code Generator

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?:(?:(public|protected|private)\\s+)|(?:(abstract|static)\\s+)|(?:(final)\\s+)|(?:(volatile|synchronized)\\s+)|(?:(native|strictfp)\\s+))*([a-zA-Z_][[:alnum:]]+)\\s+([a-zA-Z_][[:word:]<>\\[\\]]+)\\s*\\(\\s*(?:(?:([a-zA-Z_][[:word:]<>\\[\\]]+)\\s+([a-zA-Z_][[:alnum:]]+)\\s*)(?:,\\s*([a-zA-Z_][[:word:]<>\\[\\]]+)\\s+([a-zA-Z_][[:alnum:]]+)\\s*)*)?\\)\\s*\\{"; final String string = "cat\n" + "cut\n" + " cot\n" + "c@t$\n" + "c?t\n" + "c t?\n" + " caut.\n" + "caat\n" + "cuut!\n" + " hello\n" + "hello world\n" + "lite.ral $ sign\n" + "lit\\erbl ^ car[a]t\n" + "Robert\n" + "Bob\n" + "Rob\n" + "Rick\n" + "Rick\n" + "lo\n" + "lol\n" + "loll\n" + "lolll\n" + "lollll\n" + "lolllll\n" + "lollllll\n" + "lolllllll\n" + "lollllllll\n" + "lolllllllll\n" + "lollllllllll\n" + "lolllllllllll\n" + "lollllllllllll\n" + "while (a < b) { while (c < d) { --d;}; while (b < c) { ++a; --c; } }\n" + "10001\n" + "18052\n" + "19146\n" + "<b>thing</a>\n" + "+1 555-234-1234 == matches\n" + "(654) 999-0234 == matches\n" + "+1 (101) 234 9838 == matches\n" + "333 444.5555 == matches\n" + "111.234-3463 == matches\n" + "+1-333-333-3333 == doesn't match (drops the +1)\n" + "555 2341234 == doesn't match (missing a separator)\n" + "231-1115 == doesn't match (missing an area code)\n" + "doowopdoo\n" + "shoobeedoobee\n" + "doodoodoo\n" + "doowop\n" + "0\n" + "C\n" + "a@b.c\n" + "bob@bob.bob\n" + "steve@steve.co.uk\n" + "tom.jones@its.not.unusual\n" + "0.0\n" + "+.03\n" + "-100.3\n" + "4.5e5\n" + "+0.03e-9\n" + ".01e12\n" + ".e4\n" + "-.e\n\n" + "public static void main(String[] args) {\n" + " return;\n" + "}\n\n" + "private double thingDoer (int thingA , float thingB) {\n" + " while (thingA < thingB) { ++thingA; }\n" + " return thingA * thingB;\n" + "}\n\n" + "boolean blobber(){\n" + " // do blob things\n" + " return false;\n" + "}\n\n" + "invalidMethodSignature here{\n" + " return;\n" + "}\n\n" + "anotherInvalidOne(){ return; }"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html